package com.iapplize.http;

public class Base64Coder {
	// Mapping table from 6-bit nibbles to Base64 characters.
    private static char[] map1 = new char[64];
    static {
            int i = 0;
            for (char c = 'A'; c <= 'Z'; c++) {
                    map1[i++] = c;
            }
            for (char c = 'a'; c <= 'z'; c++) {
                    map1[i++] = c;
            }
            for (char c = '0'; c <= '9'; c++) {
                    map1[i++] = c;
            }
            map1[i++] = '+';
            map1[i++] = '/';
    }

    // Mapping table from Base64 characters to 6-bit nibbles.
    private static byte[] map2 = new byte[128];
    static {
            for (int i = 0; i < map2.length; i++) {
                    map2[i] = -1;
            }
            for (int i = 0; i < 64; i++) {
                    map2[map1[i]] = (byte) i;
            }
    }

    /**
     * Encodes a string into Base64 format. No blanks or line breaks are
     * inserted.
     * 
     * @param s
     *            a String to be encoded.
     * @return A String with the Base64 encoded data.
     */
    static String encodeString(String s) {
            return new String(encode(s.getBytes()));
    }
    
    /**
     * Encodes a byte array into Base64 format. No blanks or line breaks are
     * inserted.
     * 
     * @param in
     *            an array containing the data bytes to be encoded.
     * @return A character array with the Base64 encoded data.
     */
    static char[] encode(byte[] in) {
            return encode(in, in.length);
    }

    /**
     * Encodes a byte array into Base64 format. No blanks or line breaks are
     * inserted.
     * 
     * @param in
     *            an array containing the data bytes to be encoded.
     * @param iLen
     *            number of bytes to process in <code>in</code>.
     * @return A character array with the Base64 encoded data.
     */
    static char[] encode(byte[] in, int iLen) {
            int oDataLen = (iLen * 4 + 2) / 3; // output length without padding
            int oLen = ((iLen + 2) / 3) * 4; // output length including padding
            char[] out = new char[oLen];
            int ip = 0;
            int op = 0;
            while (ip < iLen) {
                    int i0 = in[ip++] & 0xff;
                    int i1 = ip < iLen ? in[ip++] & 0xff : 0;
                    int i2 = ip < iLen ? in[ip++] & 0xff : 0;
                    int o0 = i0 >>> 2;
                    int o1 = ((i0 & 3) << 4) | (i1 >>> 4);
                    int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
                    int o3 = i2 & 0x3F;
                    out[op++] = map1[o0];
                    out[op++] = map1[o1];
                    out[op] = op < oDataLen ? map1[o2] : '=';
                    op++;
                    out[op] = op < oDataLen ? map1[o3] : '=';
                    op++;
            }
            return out;
    }
    
    /**
     * Decodes a string from Base64 format.
     * 
     * @param s
     *            a Base64 String to be decoded.
     * @return A String containing the decoded data.
     * @throws IllegalArgumentException
     *             if the input is not valid Base64 encoded data.
     */
    static String decodeString(String s) {
            return new String(decode(s));
    }

    /**
     * Decodes a byte array from Base64 format.
     * 
     * @param s
     *            a Base64 String to be decoded.
     * @return An array containing the decoded data bytes.
     * @throws IllegalArgumentException
     *             if the input is not valid Base64 encoded data.
     */
    static byte[] decode(String s) {
            return decode(s.toCharArray());
    }

    /**
     * Decodes a byte array from Base64 format. No blanks or line breaks are
     * allowed within the Base64 encoded data.
     * 
     * @param in
     *            a character array containing the Base64 encoded data.
     * @return An array containing the decoded data bytes.
     * @throws IllegalArgumentException
     *             if the input is not valid Base64 encoded data.
     */
    static byte[] decode(char[] in) {
            int iLen = in.length;
            if (iLen % 4 != 0) {
                    throw new IllegalArgumentException(
                                    "Length of Base64 encoded input string is not a multiple of 4.");
            }
            while (iLen > 0 && in[iLen - 1] == '=') {
                    iLen--;
            }
            int oLen = (iLen * 3) / 4;
            byte[] out = new byte[oLen];
            int ip = 0;
            int op = 0;
            while (ip < iLen) {
                    int i0 = in[ip++];
                    int i1 = in[ip++];
                    int i2 = ip < iLen ? in[ip++] : 'A';
                    int i3 = ip < iLen ? in[ip++] : 'A';
                    if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127) {
                            throw new IllegalArgumentException(
                                            "Illegal character in Base64 encoded data.");
                    }
                    int b0 = map2[i0];
                    int b1 = map2[i1];
                    int b2 = map2[i2];
                    int b3 = map2[i3];
                    if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0) {
                            throw new IllegalArgumentException(
                                            "Illegal character in Base64 encoded data.");
                    }
                    int o0 = (b0 << 2) | (b1 >>> 4);
                    int o1 = ((b1 & 0xf) << 4) | (b2 >>> 2);
                    int o2 = ((b2 & 3) << 6) | b3;
                    out[op++] = (byte) o0;
                    if (op < oLen) {
                            out[op++] = (byte) o1;
                    }
                    if (op < oLen) {
                            out[op++] = (byte) o2;
                    }
            }
            return out;
    }

    // Dummy constructor.
    private Base64Coder() {
    }

}
